Light emitting display device including conductivity improvement layer

ABSTRACT

A method for manufacturing a light emitting display device, includes preparing a substrate having an active area and edge areas around the active area, forming a first electrode in each of a plurality of subpixels in the active area, forming a first common layer configured to cover an entirety of the active area and to have a first process margin in the edge areas outside the active area, forming a conductivity improvement layer on the first common layer in the edge areas, forming a light emitting layer in each of the subpixels, forming a second common layer having a large size than a size of the active area, on the light emitting layer, and forming a second electrode having a second process margin in the edge areas to cover at least the first common layer, on the second common layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. patent application Ser. No.16/725,829 filed on Dec. 23, 2019, which claims the priority benefit ofKorean Patent Application No. 10-2018-0173122, filed on Dec. 28, 2018 inthe Republic of Korea, the entire contents of all these applications arehereby expressly incorporated by reference as if fully set forth hereininto the present application.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a light emitting display device, andmore particularly, to a light emitting display device which changes aconfiguration of common layers to prevent light leakage generated aroundedge areas and a method for manufacturing the same.

Discussion of the Related Art

As we have recently entered the information age, the field of displayswhich visually display electrical information signals has been rapidlydeveloped and, in order to satisfy such development, various flatdisplay devices having excellent performance, such as thinness, lightweight and low power consumption, are being developed and rapidlyreplacing conventional cathode ray tube (CRT) display devices.

As examples of such flat display devices, there are a liquid crystaldisplay (LCD) device, a plasma display panel (PDP) device, a fieldemission display (FED) device, an organic light emitting diode (OLED)display device, a quantum dot display device, etc.

Among these devices, self-luminous display devices which do not requireseparate light sources and achieve compactness and clear color display,such as an organic light emitting diode display device and a quantum dotdisplay device, are considered to have competitive applications.

Such a self-luminous display device includes a light emitting devicehaving an anode and a cathode which are opposite to each other, a lightemitting layer provided between the anode and the cathode, a commonlayer related to transporting of holes and provided between the anodeand the light emitting layer, and a common layer related to transportingof electrons and provided between the cathode and the light emittinglayer, in each of subpixels provided on a substrate. Here, the commonlayers are provided to raise luminous efficiency of the light emittinglayer, and each common layer can have a multilayered structure ratherthan a monolayered structure between the corresponding electrode and thelight emitting layer.

The common layers are formed using a common mask configured to cover theentirety of an active area, and are shared by all the subpixels in theactive area. Further, in edge areas outside the active area, the commonlayer which is farthest from the cathode, which is located at theuppermost position, in the vertical direction is located at a positionclosest to the active area, and the upper common layers are configuredto cover the lower common layers thereof. The reason for this is that,since the common layer far from the cathode, for example, thehole-transporting common layer, has a high resistance component, andcauses resistance and lowers transport of electrons when it contacts thecathode, the hole-transporting common layer is formed at an inwardregion so as to avoid direct contact with the cathode.

For example, if a spacing region between the cathode and the edge of thehole-transporting common layer is not sufficient, the hole-transportingcommon layer is exposed to the outside in the edge areas, when theelectron-transporting common layer is formed after the formation of thehole-transporting common layer. Here, the formed cathode contacts thehole-transporting common layer, resistance at a region of thehole-transporting common layer directly contacting the cathode isincreased, and thus heating or abnormal light emission in the activearea adjacent to the edge areas can be caused.

Therefore, the common layers disposed in the edge areas are formed suchthat respective areas thereof are gradually increased in a verticallyupward direction.

However, if the respective common layers are formed to be spaced apartfrom each other in the edge areas, when the number of the common layersis increased, a margin area to provide a space between the common layersis increased and, in this case, an effective area actually used todisplay an image in the display device can be reduced.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a light emittingdisplay device and a method for manufacturing the same thatsubstantially obviate one or more problems due to limitations anddisadvantages of the related art.

An object of the present invention is to provide a light emittingdisplay device which changes a configuration of common layers disposedin edge areas to satisfy structural characteristics of a narrow bezeland to avoid contact between the common layer having high resistance andan electrode so as to prevent failure generated around the edge areasand thus to improve visibility, and a method for manufacturing the same.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or can be learned from practice of theinvention. The objectives and other advantages of the invention can berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, alight emitting display device includes a substrate having an active areaand edge areas around the active area, a plurality of subpixels in theactive area, an organic light emitting diode including a firstelectrode, a first common layer, a light emitting layer, a second commonlayer and a second electrode stacked at each subpixel, a first commonlayer extension configured to extend from the first common layer in theedge areas, a conductivity improvement layer configured to contact anupper surface of the first common layer extension, in the edge arealocated on at least one side of the substrate, and a second electrodeextension configured to extend from the second electrode and to overlapthe conductivity improvement layer, and provided to be closer to theedges of the edge areas than the conductivity improvement layer.

The conductivity improvement layer can be provided in the edge areaslocated at a first side and a second side of the substrate, opposite toeach other.

The conductivity improvement layer can include a p-type dopant in afirst common layer forming material.

Positions of the p-type dopant in the conductivity improvement layersprovided in the edge areas located at the first and second sides of thesubstrate can be vertically different.

The first common layer extension can directly contact another commonlayer extension between the first side and the second side of thesubstrate.

The conductivity improvement layer can lower sheet resistance of thefirst common layer extension located below the second electrodeextension in a vertical direction.

The first common layer in the active area can have a greater thicknessthan that of the first common layer extension in the edge area locatedon at least one side of the substrate.

The conductivity improvement layer can be spaced apart from the activearea.

The light emitting display device can further include a second commonlayer extension configured to extend from the second common layer andprovided in the edge areas.

The second common layer extension can contact an upper surface of theconductivity improvement layer.

A lower surface of the second common layer extension can contact upperand side surfaces of the second common layer extension.

The conductivity improvement layer can protrude closer to the outermostedge of the edge area than the second common layer extension.

A lower surface of the second electrode extension can contact upper andside surfaces of the second common layer extension and upper and sidesurfaces of the first common layer extension protruding from the secondcommon layer extension close to the outermost edge of the edge areas.

The second common layer and the second common layer extension caninclude electron-transporting or electron-injecting organic matter as amain component, and the first common layer and the first common layerextension can include hole-transporting organic matter as a maincomponent.

The light emitting display device can further include a hole-injectingdummy layer contacting lower surfaces of the first common layer and thefirst common layer extension.

The conductivity improvement layer and the hole-injecting dummy layercan include the same material.

The second common layer and the second common layer extension caninclude a plurality of layers, and the second electrode extension in theedge areas can be located closer to the outermost edges of the edgeareas than the respective layers of the second common layer extension.

In another aspect of the present invention, a method for manufacturing alight emitting display device includes preparing a substrate having anactive area and edge areas around the active area, forming a firstelectrode in each of a plurality of subpixels in the active area,forming a first common layer configured to cover the entirety of theactive area and to have a first process margin in the edge areas outsidethe active area, and forming a conductivity improvement layer on thefirst common layer in the edge areas, forming a light emitting layer ineach of the subpixels, forming a second common layer having a large sizethan a size of the active area, on the light emitting layer, and forminga second electrode having a second process margin in the edge areas tocover at least the first common layer, on the second common layer.

The second process margin can be outside the first process margin, andan edge of the second common layer extension can be inside the firstprocess margin or the second process margin.

The forming the first common layer and the forming the conductivityimprovement layer can be carried out in the same chamber, a first commonlayer material deposition source and p-type dopant material depositionsources can be disposed adjacent to one another, and closing the p-typedopant material deposition sources, when the active area of thesubstrate corresponds to the p-type dopant material deposition sources,and opening the p-type dopant material deposition sources to supply ap-type dopant, when a first edge area of the substrate corresponds tothe p-type dopant material deposition sources.

The p-type dopant material deposition sources can include a first p-typedopant material deposition source and a second p-type dopant materialdeposition source disposed at both sides of the first common layermaterial deposition source, and the supply of the p-type dopant can becarried out corresponding to first common layer material supply startingpart and ending part of the substrate from the first common layermaterial deposition source.

The method can further include forming a hole-injecting dummy layer inthe chamber, just before the forming the first common layer.

The forming the hole-injecting dummy layer can include depositing thehole-injecting dummy layer just before the forming the first commonlayer by opening a hole-injecting material deposition source, disposedadjacent to the first common layer material deposition source configuredto supply a first common layer material in the chamber, before theactive area of the substrate corresponds to the first common layerdeposition source.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with descriptions to explain the principle of the invention. Inthe drawings:

FIG. 1A is a plan view of a light emitting display device in accordancewith a first embodiment of the present invention.

FIG. 1B is a plan view of a light emitting display device in accordancewith a modification of the first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line I-I′ of one of FIGS.1A and 1B.

FIG. 3 shows cross-sectional views of an organic stack in an active areaand an organic stack in edge areas at regions A and B of FIG. 2 .

FIGS. 4A and 4B are cross-sectional views illustrating configurations ofcommon layers in the edge areas of the light emitting display devices inaccordance with the first embodiment of the present invention and themodification thereof.

FIGS. 5A and 5B are respectively a plan view and a cross-sectional viewillustrating edge areas of a light emitting display device in accordancewith a comparative example.

FIG. 6A is a photograph representing the light emitting display devicein accordance with the comparative example in normal driving of bluelight emitting diodes.

FIG. 6B is a photograph representing the light emitting display devicein accordance with the comparative example in abnormal driving of bluelight emitting diodes, when an electron transport layer having a smallerarea than that of a hole transport layer is formed in edge areas andthus the hole transport layer directly contacts a second electrode.

FIG. 7 is a cross-sectional view illustrating a configuration of edgeareas of a light emitting display device in accordance with a secondembodiment of the present invention.

FIGS. 8A to 8C are cross-sectional views illustrating measurement ofsheet resistances of light emitting display devices in accordance withfirst to third test examples.

FIG. 9 is a graph representing the sheet resistances of the lightemitting display devices in accordance with the first to third testexamples.

FIGS. 10A to 10C are band diagrams of the light emitting display devicesin accordance with the first to third test examples.

FIGS. 11A to 11E are process views illustrating a method for forming afirst common layer and a conductivity improvement layer of the lightemitting display device in accordance with the present invention.

FIGS. 12A to 12E are views illustrating arrangements of depositionsources respectively used in operations of FIGS. 11A to 11E.

FIG. 13A is a cross-sectional view illustrating a structure of the edgearea corresponding to deposition materials in the initial stage of adeposition process, after completion of the operation of FIG. 11E.

FIG. 13B is a cross-sectional view illustrating a structure of theactive area, after completion of the operation of FIG. 11E.

FIG. 13C is a cross-sectional view illustrating a structure of the edgearea corresponding to the deposition materials in the final stage of thedeposition process, after completion of the operation of FIG. 11E.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. However, the present invention can be embodied in manyalternative forms and should not be construed as limited to theembodiments set forth herein, and the embodiments of the presentinvention are provided only to completely disclose the invention and tocompletely inform those skilled in the art of the scope of theinvention. Further, the names of elements used in the followingdescription of the embodiments of the present invention are selected inconsideration of ease in preparation of the specification, and can thusdiffer from the names of parts of an actual product.

Shapes, sizes, rates, angles, numbers, etc. disclosed in the drawings todescribe the embodiments of the present invention are only exemplary anddo not limit the present invention. In the following description of theembodiments and the drawings, the same or similar elements are denotedby the same reference numerals even though they are depicted indifferent drawings. In the following description of the embodiments ofthe present invention, a detailed description of known functions andconfigurations incorporated herein will be omitted when it can make thesubject matter of the present invention rather unclear. In the followingdescription of the embodiments, the terms ‘including’, ‘having’,‘consisting of’, etc., will be interpreted as indicating presence of oneor more other characteristics, numbers, steps, operations, elements orparts stated in the specification or combinations thereof, and do notexclude presence of characteristics, numbers, steps, operations,elements, parts or combinations thereof, or possibility of adding thesame, unless the term ‘only’ is used. It will be understood that asingular expression of an element includes a plural expression of theelement unless stated otherwise.

In interpretation of elements included in the various embodiments of thepresent invention, it will be interpreted that the elements includeerror ranges even if there is no clear statement.

In the following description of the embodiments, it will be understoodthat, when positional relations are expressed, for example, when anelement is ‘on’, ‘above’, ‘under’, ‘beside’, etc., another element, thetwo elements can directly contact each other, or one or more otherelements can be interposed between the two elements unless the term‘just’ or ‘directly’ is used.

In the following description of the embodiments, it will be understoodthat, when temporal relations are expressed, for example, a termexpressing a sequence of events, such as ‘after’, ‘subsequent to’, ‘nextto’ or ‘before’ can encompass continuous relationship between theevents, or discontinuous relationship between the events unless the term‘just’ or ‘directly’ is used.

In the following description of the embodiments, it will be understoodthat, when the terms ‘first’, ‘second’, etc. are used to describevarious elements, these terms are used merely to discriminate the sameor similar elements. Therefore, an element modified by the term ‘first’can be the same as an element modified by the term ‘second’ within thetechnical scope of the invention unless stated otherwise.

Characteristics of the various embodiments of the present invention canbe partially or entirely connected to or combined with each other andtechnically variously driven and interlocked with each other, and thevarious embodiments can be independently implemented or be implementedtogether in connection with each other.

A light emitting display device in accordance with one or more examplesof the present invention is a self-luminous display device, whichincludes a light emitting device (light emitting diode) performing lightemission in each of a plurality of subpixels on a substrate, forexample, an organic light emitting diode display device or a quantum dotdisplay device.

Although the accompanying drawings exemplarily illustrate an organiclight emitting diode display device as the light emitting displaydevice, a quantum dot light emitting display device can be implementedby substituting a quantum dot light emitting layer for a light emittinglayer of the organic light emitting diode display device and includingthe same stack structure and conductivity improvement layer as theorganic light emitting diode display device.

Hereinafter, the light emitting display device in accordance with one orembodiments of the present invention will be described with reference tothe accompanying drawings. All the components of the light emittingdisplay device according to all embodiments of the present invention areoperatively coupled and configured.

FIG. 1A is a plan view of a light emitting display device in accordancewith a first embodiment of the present invention, FIG. 1B is a plan viewof a light emitting display device in accordance with a modification ofthe first embodiment of the present invention, and FIG. 2 is across-sectional view taken along line I-I′ of one of FIGS. 1A and 1B.

As exemplarily shown in FIGS. 1A to 2 , the light emitting displaydevice in accordance with an example of the present invention includes asubstrate 100 having an active area AA (an area inside a dotted line)and edge areas NA around the active area AA (an area outside the dottedline), a plurality of subpixels RP, GP and BP provided in the activearea AA, each subpixel having an organic light emitting diode OLED(e.g., shown on the right side of FIG. 3 ) formed by stacking a firstelectrode 110, a first common layer 120, a light emitting layer 140: 140r, 140 g or 140 b, a second common layer 150 and a second electrode 160,a first common layer extension 120 a extending from the first commonlayer 120 to be provided in the edge areas NA, a conductivityimprovement layer 119 b provided on the first common layer extension 120a, and a second electrode extension 160 a extending from the secondelectrode 160 to be provided in the edge areas NA and to overlap theconductivity improvement layer 119 b and located to be closer to theedges of the edge areas NA than the conductivity improvement layer 119 b(referring to FIG. 2 ).

Further, in the following description of the embodiments of the presentinvention, the ‘edge areas NA’ preferably can mean areas around theactive area NA, which are shielded by other parts or devices and areprovided at the edges of the substrate 100 to have a designated width,and some of extensions of the elements of the organic light emittingdiode OLED or wirings are disposed in the edge areas NA. The edge areasNA are not used in display and can thus also be referred to asnon-display areas NA.

In the light emitting display device in accordance with one or moreembodiments of the present invention, particularly as exemplarily shownin FIGS. 1A and 2 , by providing the conductivity improvement layer 119b on the first common layer extension 120 a in the edge areas NA, thesecond common layer(s) 150 formed after formation of the first commonlayer 120 and the first common layer extension 120 a can have no processmargin or a minimal process margin so that exposure of the first commonlayer extension 120 a in the edge areas NA is prevented in formation ofthe second common layer(s) 150, and even if a second common layerextension 150 a is formed farther inward than the first common layerextension 120 a, the conductivity improvement layer 119 b and the secondelectrode extension 160 a are connected and thus direct contact betweenthe second electrode extension 160 a and the first common layerextension 120 a having high resistance is prevented.

In the description of the embodiments of the present invention, ‘processmargin’ can preferably mean a width of a corresponding layer to beformed which protrudes farther outward than a lower layer providedthereunder.

In the present invention, the first common layer extension 120 a, thesecond common layer extension 150 a and the second electrode extension160 a are provided in the edge areas NA which do not actually contributeto light emission and are thus referred to as extensions, and the firstcommon layer extension 120 a, the second common layer extension 150 aand the second electrode extension 160 a respectively extend integrallyfrom the first common layer 120, the second common layer 150 and thesecond electrode 160.

As the size of the edge areas NA is increased, an ineffective area whichdoes not contribute to display is increased, and thus, research ondecrease in the size of the edge areas NA is underway in terms ofincrease in the effective area in the light emitting display device.

In the light emitting display device, when the light emitting diodeincluding the stack of the first and second electrodes disposed oppositeto each other, the common layers and the emitting layers providedbetween the first and second electrodes is formed, different masks areapplied to formation of respective layers and process margins areapplied to the respective layers in consideration alignment errorsbetween the layers. Provisions of such process margins is an obstacle toreduction in the above-described ineffective area, and thus the lightemitting display device in accordance with the present invention changesa configuration of the edge areas so as to reduce the process margins,and generates no failure even if an alignment error between the layersoccurs.

In general, common layers in a light emitting display device are layerswhich are formed in common so as to cover the entirety of an activearea. In a light emitting display device in accordance with acomparative example and known light emitting display devices, commonlayers are formed to have different process margins, respectively, andare configured such that areas of the respective common layers aregradually increased in an upward direction and thus an upper commonlayer and a second electrode cover a lower common layer. However, inthis case, when the respective common layers have the different processmargins, an area occupied by the process margins in the edge areas isincreased, and thereby an ineffective area is increased. Therefore, thelight emitting display device in accordance with the present inventionfurther includes the conductivity improvement layer 119 b in the edgeareas, thus having a configurational difference with the light emittingdisplay device in accordance with the comparative example.

The first common layer extension 120 a overlaps the edge area NA by afirst interval c from the edge of the active area AA. The first intervalc is a value in consideration of an alignment error when a depositionmask and a deposition source are aligned to form the first common layer120, and the first interval c has a small value when the alignment erroris small and has a large value when the alignment error is large. Forexample, if the light emitting display device is a small terminal, suchas a mobile terminal, a smart watch or an e-book, the first interval ccan be about 100 μm or less.

The first common layer 120 is a hole transport related common layer, andthe second common layer 150 is an electron transport related commonlayer. Each of these common layers 120 and 150 can have a multilayeredstructure from the point of view of efficiency improvement and lifespanimprovement. In most cases, other than a hole-transporting layer and anelectron-transporting layer, layers subsidiarity assisting efficiencyimprovement and lifespan improvement have smaller thicknesses that thoseof the hole-transporting layer and the electron-transporting layer.

Through the first common layer extension 120 a, if an alignment error ofa designated value occurs during formation of the hole-transportingfirst common layer 120 in the respective light emitting diodes in theactive area AA, the first common layer 120 can sufficiently cover theactive area AA even though a shift in a leftward or rightward directionor in an upward or downward direction occurs. In a subpixel in which thehole-transporting first common layer 120 is not provided between thefirst electrode and the second electrode of the light emitting diode,hole transport is not normally carried out, and thus recombination ofelectrons and holes in the corresponding light emitting layer is noteffectively carried out due to delay of hole transport, or the like.Therefore, the first common layer extension 120 a which is formedintegrally with the first common layer 120 is provided to have the firstinterval c, in consideration of the process margin thereof correspondingto the edge areas NA in design.

In the light emitting display device in accordance with one or moreembodiments of the present invention, the conductivity improvement layer119 b is provided to directly contact the upper surface of the firstcommon layer extension 120 a. The conductivity improvement layer 119 bcan be formed of a material having resistance lower than at least one ofthe first common layer 120 and the first common layer extension 120 a,be formed on the upper surface of the first common layer extension 120 aduring the same process as formation of the first common layer 120 andthe first common layer extension 120 a, and have a shape surrounding theedge of the first common layer extension 120 a, as exemplarily shown inFIG. 1A. Otherwise, although the conductivity improvement layer 119 bcan be formed on the entire area of the first common layer extension 120a in the edge areas NA, the conductivity improvement layer 119 b can berestrictively formed on some regions of the area of the first commonlayer extension 120 a. Here, if the edge areas NA include first tofourth edge areas NA1, NA2, NA3 and NA4 located at left, lower, rightand upper sides of the substrate 100 based on the active area AA, theconductivity improvement layer 119 b can be located in the first andthird edge areas NA1 and NA3. Therefore, the conductivity improvementlayer 119 b can have discontinuities in the formation region thereof.

In this case, the conductivity improvement layer 119 b can be formedwithin a region where the first common layer extension 120 a is located,i.e., within the first interval c, so as to equivalent to efficiency ofthe light emitting diodes in the active area without change in the stackstructure of the light emitting diodes.

Although the target of the conductivity improvement layer 119 b is to beformed within the first interval c, as circumstances require, asdeposition is performed while moving a deposition sources or thesubstrate 100, a material for the conductivity improvement layer 119 bcan remain to have a smaller thickness than the thickness of theconductivity improvement layer 119 b in some regions of the active areaAA adjacent to the edge areas NA due to continuity of deposition. Theconductivity improvement layer 119 b is formed to have a small thicknessof about 30 Å or less, corresponding to 1/10 to 1/000 of the thicknessof the first common layer 120, and does not significantly influence thefunction of the light emitting diodes in the remaining active area AA.

The first interval is smaller than the width of the edge areas NA, andthe edge of the common layer extension 120 a is located farther inwardthan the edge of the substrate 100 and is spaced apart from the edge ofthe substrate 100. This means that elements to cover the upper surfaceof the first common layer extension 120 a are provided outside the firstcommon layer extension 120 a in the edge areas NA and, for example,these elements can be the second electrode 160, a capping layer 170 andan encapsulation part 200.

In the light emitting display device in accordance with one or moreembodiments of the present invention, the second common layer 150 isformed in the active area AA after formation of the light emittinglayers 140: 140 r, 140 g and 140 b. When the second common layer 150 isformed, the second common layer extension 150 a formed integrally withthe second common layer 150 can be provided in the edge areas NA. In thelight emitting display device in accordance with the comparativeexample, a second common layer is formed to have a large process marginso that the second common layer has a greater size than a first commonlayer so as to avoid direct contact between the first common layer and asecond electrode, but, in the light emitting display device inaccordance with the present invention, the second common layer extension150 a can be formed to have a size similar to or less than that of thefirst common layer extension 120 a. In the latter case, even if thefirst common layer extension 120 a is exposed farther outward than thesecond common layer extension 150 a and thus the second electrode 160and the conductivity improvement layer 119 b directly contact eachother, sheet resistance of the second electrode 160 is not increased dueto the conductivity improvement layer 119 b which surrounds the activearea AA along the edge line of the first common layer extension 120 aand is in area contact with the first common layer extension 120 a.Further, the conductivity improvement layer 119 b steals electrons fromthe first common layer extension 120 a provided thereunder due toelectron withdrawing characteristics of the conductivity improvementlayer 119 b, and thereby, the first common layer extension 120 a and thefirst common layer 120 formed integrally therewith lack electrons, holesare generated in electron vacancies, and carrier mobility to the lightemitting layers 140 of the light emitting diodes in the active area AAand conductivity of the light emitting diodes are improved.

As exemplarily shown in FIG. 2 , a hole-injecting dummy layer 119 a canbe further formed under the hole-transporting first common layer 120 andfirst common layer extension 120 a. The hole-injecting dummy layer 119 acan be formed as a separate layer independently of the first commonlayer 120 and the first common layer extension 120 a to be providedthereunder, or be formed by doping a hole-transporting material of thelower portions of the first common layer 120 and the first common layerextension 120 a with about 1-20 wt % of a hole-injecting material. Here,the lower portions of the first common layer 120 and the first commonlayer extension 120 can be portions thereof corresponding to less than ½of the total thickness of the first common layer extension 120 a, andparticularly, be portions thereof corresponding to ⅕ or less to 1/20 orless of the total thickness of the first common layer extension 120 a.The hole-injecting dummy layer 119 a and the conductivity improvementlayer 119 b are formed before and after formation of the first commonlayer 120 and the first common layer extension 120 a, using the samemask in the same chamber as formation of the first common layer 120 andthe first common layer extension 120 a, and are formed by doping amaterial to form the first common layer 120 with a conductivityimproving material having lower resistance than the first common layer120. For example, the conductivity improving material can be a p-typedopant. As circumstances require, the conductivity improvement layer 119b can be formed of a material for the conductivity improvement layer 119b having excellent p-type characteristics which is more effective toimprove conductivity, which is different from a material for thehole-transporting dummy layer 119 a. In the latter case, theconductivity improvement layer 119 b having a different materialcomposition from that of the hole-injecting dummy layer 119 a can beformed using a conductivity improving material deposition source to formthe conductivity improvement layer 119 b which is separately provided.The hole-injecting dummy layer 119 a contacts the lower surfaces of thefirst common layer extension 120 a and the first common layer 120, andthe conductivity improvement layer 119 b contacts the upper surface ofthe first common layer extension 120 a. As circumstances require, thehole-injecting dummy layer 119 a is not provided as a separate layer,and can be included in the lower portions of the first common layer 120and the first common layer extension 120 a by co-depositing thehole-transporting material and the hole-injecting material at an initialstage of formation of the first common layer 120 and the first commonlayer extension 120 a. Further, if the hole-injecting dummy layer 119 ais omitted, as such, the hole-injecting material can function as a kindof dopant included in the first common layer 120.

The first common layer 120 in the active area AA, on which theconductivity improvement layer 119 b is not formed (referring to regionA of FIG. 2 ), is formed by blocking supply of the conductivityimproving material and continuously supplying the hole-transportingmaterial, and can have a greater thickness than that of the first commonlayer extension 120 a (referring to region B of FIG. 2 ) in the edgeareas NA.

The second common layer extension 150 a formed in the edge areas NAintegrally with the second common layer 150 formed after formation ofthe light emitting layers 140: 140 r, 140 g and 140 b can have a smallerarea than that of the first common layer extension 120 a, and in severecases, no second common layer extension 150 a can be provided in theedge areas NA. That is, the second common layer extension 150 a inaccordance with the present invention can have no process margin so asnot to protrude outward from the first common layer extension 120 a.Therefore, the second electrode extension 160 a formed integrally withthe second electrode 160, which is the uppermost element of the lightemitting diode, can be connected to the upper and side surfaces of thefirst common layer extension 120 a protruding farther outward than thesecond common layer extension 150 a (with reference to FIG. 4B).

The second electrode 160 is also formed to cover the entirety of theactive area AA and the second electrode extension 160 a protrudes to theedge areas NA, in the same manner as the first and second common layerextensions 120 a and 150 a, and receives an electrical signal throughsignal connection lines 114 in a thin film transistor array providedunder the edge areas NA. The signal connection lines 114 are connectedto pad electrodes 116, and the pad electrodes 116 at the edges of theedge areas NA are exposed and connected to a printed circuit board (PCB)or a flexible printed circuit board (FPCB).

The pad electrodes 116 can be located at any one side of the substrate100. In addition to the pad electrodes 116 to transmit a signal to thesecond electrode 160, a plurality of pad electrodes used to transmit asignal to wirings of the thin film transistor array can be furtherprovided. For convenience in connection to the printed circuit board(PCB) or the flexible printed circuit board (FPCB), these pad electrodescan be configured to be adjacent to each other. A region in which thepad electrodes are provided to be adjacent to each other in the edgeareas NA of the substrate 100 is referred to as a pad part PAD.

The substrate 100 can have a rectangular shape, as exemplarily shown inFIGS. 1A and 1B, or have an atypical shape, such as an asymmetricalshape or a partially curved shape, as needed. The light emitting displaydevice in accordance with the present invention can be defined on thesubstrate 100 having any shape, and be characterized in that theconductivity improvement layer 119 b is formed on the upper surface ofthe first common layer extension 120 a in the edge areas NA of thesubstrate 100. The conductivity improvement layer 119 b can be formed atall edges of the substrate 100, as exemplarily shown in FIG. 1A, or beformed at both side edges of the substrate 100, as exemplarily shown inFIG. 1B.

The first common layer 120 and the first common layer extension 120 acan be integrally formed of the same material, i.e., thehole-transporting material, for example, one or more selected from thegroup consisting ofN,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine(NPD), N,N′-bis-(3-methylphenyl)-N,N′-bis-(phenyl)-benzidine (TPD) and(2,2′7,7′tetrakis(N,N-diphenylamino)-9,9′-spirofluorene (Spiro-TAD).However, since one of the main objects of the first common layer 120 andthe first common layer extension 120 a is to have a hole transportingfunction, the first common layer 120 and the first common layerextension 120 a are not limited to the above-described materials and canbe formed of any hole-transporting organic material.

As the material to form the conductivity improvement layer 119 b, amaterial having lower resistance than that of the first common layer 120and the first common layer extension 120 a can be included as a dopantin the material for the first common layer 120, and can be, for example,a p-type dopant or an organic material having high conductivity, whichcan lower resistance of an electrode contacting the same.

For example, the organic material having high conductivity to form theconductivity improvement layer 119 b can be one of p-type dopantsexpressed as chemical formulas 1 to 4.

However, in addition to the materials expressed as chemical formulas 1to 4, the conductivity improvement layer 119 b can be formed of anymaterial which can have lower resistance than the hole-transportingmaterial to form the first common layer 120 and excellent conformabilitywith the first common layer 120 and can lower resistance of a layerconnected thereto.

The first common layer 120 can include a hole injection layer, a holetransport layer, an electron blocking layer, etc. The first common layer120 essentially includes the hole transport layer, and can furtherinclude additional layers having other characteristics. In the presentinvention, the first common layer 120 and the first common layerextension 120 a have planar continuity without disconnection but have athickness difference according to areas, and the first common layer 120and the first common layer extension 120 a are different in that theconductivity improvement layer 119 b is further formed on the firstcommon layer extension 120 a located in the edge areas NA. For example,even if an additional hole transport-related layer, such as the electronblocking layer, is further formed on the hole transport layer, theconductivity improvement layer 119 b can be further provided inselective areas, i.e., the edge areas NA, on the hole transport-relatedlayer of the first common layer extension 120 a formed integrally fromthe first common layer 120 in the active area AA without disconnection,and thus lower resistance of the hole transport-related layer.

The second common layer 150 and the second common layer extension 150 awhich are formed integrally can include a hole blocking layer, anelectron transport layer, an electron injection layer, etc. The secondcommon layer 150 and the second common layer extension 150 a essentiallyinclude the electron transport layer, and can further include additionallayers having other characteristics. Further, the second common layer150 can be formed of, for example, an anthracene-based compound, andfurther include a dopant to adjust electron mobility and a barrier withan adjacent layer thereto, as needed.

Each of a plurality of subpixels provided in the active area AA includesan organic light emitting diode OLED, and the organic light emittingdiode is formed by stacking the first electrode 110, the first commonlayer 120, the light emitting layer 140, the second common layer 150 andthe second electrode 160. The respective subpixels can include the redlight emitting layer 140 r, the green light emitting layer 140 g and theblue light emitting layer 140 b according to colors of light emitted bythe subpixels, as exemplarily shown in FIG. 2 . Light emitting layers ofother colors than the above-described colored light emitting layers 140r, 140 g and 140 b can be provided according to colors of light emittedby the subpixels. Since these light emitting layers 140 r, 140 g and 140b are formed using fine metal masks (FMM) provided with fine openingsaccording to respective colors, the light emitting layers 140 r, 140 gand 140 b can be selectively formed in the active area AA except for theedge areas NA, and do not have extensions in the edge areas NA and thusdo not increase the edge areas NA.

As circumstances require, color filters can be further provided todivide colors of the respective subpixels instead of provision ofdifferent light emitting layers. Here, a color filter layer can befurther provided on or under the light emitting diodes to be close to alight emitting side, and the light emitting diodes of the respectivesubpixels can include a white light emitting stack having the sameconfiguration. In this case, the respective subpixels can include thesame white light emitting layer, or include plural different coloredlight emitting stacks which are stacked so as to finally emit whitelight through the light emitting diodes. In any case, in the lightemitting display device in accordance with the present invention, theconductivity improvement layer 119 b is provided on the upper surface ofthe first common layer extension 120 a which is initially formed, andthus, the second common layer 150 (and the common layer extension 150 a)which is subsequently formed can have no process margin. Since processmargins according to layers are provided in the edge areas NA, increasein the size of the edge areas NA can be prevented. Respective layers ofsuch a white light emitting stack are formed in common in the activearea AA using a common mask other than a fine metal mask, and, afterformation of the hole-transporting first common layer 120 next toformation of the first electrode 110, the conductivity improvement layer119 b is formed and then, even if a plurality of light emitting layersis vertically provided, the light emitting layers are formed inside thefirst common layer extension 120 a without process margins in the edgeareas NA.

A bank 115 is provided among the subpixels RP, GP and BP, and can thusdefine regions in which light is emitted by the respective lightemitting diodes, through openings thereof. A dam pattern formed of thesame material as the bank 115 can be further provided in the edge areasNA and can thus prevent a material in a liquid state from overflowingthe dam pattern during a manufacturing process.

Further, as exemplarily shown in FIG. 2 , the substrate 100 can includethe thin film transistor array provided between the substrate 100 andthe organic light emitting diodes.

The thin film transistor array includes thin film transistors TFTsconnected to the organic light emitting diodes OLEDs in the respectivesubpixels in the active area AA.

The thin film transistor TFT includes a semiconductor layer 102, a gateelectrode 104 overlapping the semiconductor layer 102 to define achannel region, and a drain electrode 106 and a source electrode 107connected to both sides of the semiconductor layers 102.

The semiconductor layer 102 can be formed of an amorphous silicon layer,a crystalline silicon layer or an oxide semiconductor layer, and, ascircumstances require, two or three layers of the above-described layerscan be stacked.

A gate insulating film 103 is provided between the gate electrode 104and the semiconductor layer 102. Further, a buffer layer 101 to preventeffect of a process of removing elements from the lower surface of thesubstrate 100 or penetration of impurities from the substrate 100 can befurther provided between the semiconductor layer 102 and the substrate100. As circumstances require, the buffer layer 101 can be omitted.

Further, wirings, such as gate lines connected to the gate electrodes104 and extending in one direction, data lines connected to the sourceelectrodes 107 and disposed in a direction intersecting the gate lines,a power supply line, etc., can be further provided on the substrate 100.

The thin film transistor array in the edge areas NA can further includethe signal connection lines 114 formed through the same process asformation of the gate electrodes 104, and the pad electrodes 116connected to the signal connection lines 114 and formed through the sameprocess as formation of the source electrodes 107 and the drainelectrodes 106.

Here, reference numeral 105 indicates an interlayer insulating film,reference numeral 108 indicates an inorganic protective film, referencenumeral 109 indicates an organic protective film, and these films 105,108 and 109 are provided to insulate wirings of different layers inregions which are not connected.

Further, the organic light emitting diode OLED can further includes thecapping layer 170 to protect the surface of the second electrode 160 andto improve light extraction. The capping layer 170 can be formed of ahole-transporting material of the same series as or a similar series tothe first common layer 120 of the organic light emitting diode OLED, orbe formed by stacking such a hole-transporting material and an inorganicmaterial. Further, in order to improve light extraction, the stackedlayers can have a designated refractive index difference.

Further, the encapsulation part 200 is provided on the upper surface ofthe capping layer 170 to cover the capping layer 170 so as to protect anarray of the organic light emitting diodes OLEDs. The encapsulation part20 essentially includes a first inorganic film 210, an organic film 220and a second inorganic film 230, and can further include one or morepairs of a stack of an inorganic film and an organic film providedthereon. The first and second inorganic films 210 and 230 of theencapsulation part 200 protrude farther outward than the organic film220 in the edge areas NA so as to directly meet outdoor air, and is thuseffective in preventing transmission of external moisture.

The organic film 220 can have a greater thickness than any layerincluded in the thin film transistor array or the organic light emittingdiode array, sufficient to prevent movement of particles generated inprocesses, and therefore, after formation of the organic film 220, thesurface of the organic film 220 is planarized due to thesecharacteristics. In order to exhibit such an effect, the organic film220 can have a thickness which is 5 times to 20 times the thicknesses ofthe first and second inorganic films 210 and 230. The encapsulation part200 including the first inorganic film 210, the organic film 220 and thesecond inorganic film 230 can be formed to expose the pad electrodes 116at the side of the substrate 100 where the pad part PAD is located, andthe first and second inorganic films 210 and 230 can be formed to theedges of the substrate 100 at other sides of the substrate 100 where thepad part PAD is not located.

The encapsulation part 200 extends to the edges of the substrate 100 inregions except for the pad part PAD, and is configured to expose the padelectrodes 116 in the pad part PAD so that the pad electrodes 116 can beconnected to the printed circuit board after formation of theencapsulation part 200.

The substrate 100 can employ, for example, a hard glass substrate, aplastic substrate or a plastic film which is bendable.

Further, as exemplarily shown in FIGS. 1A and 1B, a set of a redsubpixel RP, a green subpixel GP and a blue subpixel BP can constituteone pixel P. Such a pixel P is repeated into a matrix on the substrate100 in the active area AA. Although the illustrated example representsthe red, green and blue subpixels RP, GP and BP, the pixel P is notlimited thereto and can include a combination of subpixels to emit othercolors of light, such as yellow, magenta, cyan, etc. As circumstancesrequire, in addition to the illustrated colored subpixels RP, GP and BP,the pixel can further include a white subpixel.

Division of the respective subpixels can be achieved according to colorsof light emitted by the subpixels. Colors of emitted light can beacquired by varying the configuration of the light emitting layers inthe organic light emitting diodes OLEDs, or by providing a color filterlayer close to light emitting sides of the organic light emitting diodesOLEDs while emitting light of the same color through the organic lightemitting diodes OLEDs. If the respective subpixels have different lightemitting layers to emit different colors of light, the respective lightemitting layers 140 r, 140 g and 140 b are located to be spaced apartfrom one another, as exemplarily shown in FIG. 2 .

FIG. 3 shows cross-sectional views of an organic stack in the activearea (A) and an organic stack in the second and fourth edge areas (B′).

As exemplarily shown in FIG. 1B, if the conductivity improvement layer119 b is formed in the first and third edge areas NA1 and NA3 and is notformed in the second and fourth edge areas NA2 and NA4, organic stacksin the two edge areas have different structures (referring to B of FIG.2 and B′ of FIG. 3 ). As exemplarily shown in B′ of FIG. 3 , during aprocess of forming the first common layer 120 after formation of thehole-injecting dummy layer 119 a, in the second and fourth edge areasNA2 and NA4, the second common layer extension 150 a is located directlyon the first common layer extension 120 a, and the second electrodeextension 160 a is located to cover the upper and side surfaces of thesecond common layer extension 150 a and the side surface of the firstcommon layer extension 120 a. In this case, an organic stack B′ in thesecond and fourth edge areas NA2 and NA4 has the same configuration ofthe common layers as an organic stack A in the active area AA exceptthat the organic stack B′ does not have the light emitting layer 140.

Hereinafter, the configuration of the edge areas of the above-describedlight emitting display device in accordance with the present inventionwill be described in more detail.

FIGS. 4A and 4B are cross-sectional views illustrating configurations ofcommon layers in edge areas of the light emitting display devices inaccordance with the first embodiment of the present invention and themodification thereof.

As exemplarily shown in FIG. 4A, in the light emitting display device inaccordance with the first embodiment of the present invention, thehole-transporting dummy layer 119 a, the first common layer extension120 a, the conductivity improvement layer 119 b, the second common layerextension 150 a and the second electrode extension 160 a aresequentially located on the bank 115 in the edge areas NA. Here, sincethe hole-injecting dummy layer 119 a, the first common layer extension120 a, and the conductivity improvement layer 119 b can be formed usingthe same mask in the same chamber, the edges thereof can coincide withone another.

Further, the second common layer extension 150 a can be formed without aprocess margin, and have the same width as the first common layerextension 120 a, as exemplarily shown in FIG. 4A, or can be formedfarther inward than the first common layer extension 120 a, asexemplarily shown in FIG. 4B. If interlayer misalignment is severe, thesecond common layer extension 150 a may not be provided in the edgeareas NA and, in this case, the conductivity improvement layer 119 bprotruding farther outward than the second common layer extension 150 ameets the second electrode extension 160 a, prevents increase inresistance of the second electrode 160 and thus prevents lowering ofluminance according to respective regions.

A width of an overlapping region between the first common layerextension 120 a and the conductivity improvement layer 119 b is referredto as a first width d, and the first width d is included in the firstinterval c (referring to FIG. 1 ) in the edge areas NA, occupied by thefirst common layer extension 120 a. If the first width d is greatest,the conductivity improvement layer 119 b can be formed to occupy theentirety of the first interval corresponding to the width of the firstcommon layer extension 120 a.

The second electrode extension 160 a is formed to protrude fartheroutward than the first common layer extension 120 a by a second intervala so as to cover all the side surfaces of the second common layerextension 150 a, the conductivity improvement layer 119 b, the firstcommon layer extension 120 a and the hole-injecting dummy layer 119 a.The light emitting display device can further include protrusionsconnected to the signal connection lines 114 located under the pad partPAD. Although not shown in the drawings, contact holes can be providedin some regions in which the second electrode extension 160 a and thebank 115 overlap, and connection with wirings located under the secondelectrode extension 160 a and the bank 150 to transmit ground voltage orphase voltage can be carried out through the contact holes. Here, thewirings to transmit ground voltage or phase voltage can be connected topad electrodes disposed in the same layer as the wirings or in adifferent layer from the wirings.

In the light emitting display device in accordance with the presentinvention, since common layers formed after formation of theconductivity improvement layer 119 b can be formed without processmargins, when the organic light emitting diodes OLEDs are formed, onlythe first interval c of the first common layer extension 120 a and thesecond interval a of the second common layer extension 160 a areprovided as extensions in the edge areas NA, and thus the width of theedge areas NA can be remarkably reduced, as compared to the lightemitting display device in accordance with the comparative example, inwhich respective common layers are configured to gradually protrudefarther outward than the lower layers thereof in the edge areas.

Although FIGS. 4A and 4B illustrate the bank 115 as protruding from thesecond electrode extension 160 a by a third interval b, this structureis not essential and the third interval b can be omitted, ascircumstances require.

The conductivity improvement layer 119 b contacts the upper surface ofthe first common layer extension 120 a, and thus serves to avoid directcontact between the first common layer extension 120 a having highresistance and other elements.

Further, the conductivity improvement layer 119 b can be spaced apartfrom the active area AA. The conductivity improvement layer 119 isrestrictively provided only in the edge areas NA, so as to preventinfluence on driving of the organic light emitting diodes OLEDs.

If the second common layer extension 150 a extending from the secondcommon layer 150 is further provided in the edge areas NA, the secondcommon layer extension 150 a can contact the upper surface of theconductivity improvement layer 119 b.

As exemplarily shown in FIG. 4A, the lower surface of the secondelectrode extension 160 a can contact the upper and side surfaces of thesecond common layer extension 150 a.

As exemplarily shown in FIG. 4B, the conductivity improvement layer 119b can protrude to be closer to the edges of the edge areas NA than thesecond common layer extension 150 a.

The lower surface of the second electrode extension 160 a can contactthe upper and side surfaces of the second common layer extension 150 aand the upper and side surfaces of the first common layer extension 120a protruding from the second common layer extension 150 a to be close tothe edges of the edge areas NA.

The second common layer 150 and the second common layer extension 150 acan include electron-transporting or electron-injecting organic matteras a main component, and the first common layer 120 and the first commonlayer extension 120 a can include hole-transporting organic matter as amain component.

The conductivity improvement layer 119 b can include the above-describedp-type dopant as organic matter having a LUMO (Lowest UnoccupiedMolecular Orbital) level which has a difference with a work function ofthe first electrode 110 by 1.5 eV or less. The p-type dopant can be anorganic material.

The conductivity improvement layer 119 b can lower sheet resistance ofthe first common layer extension 120 a located in the vertical directionof the second electrode extension 160 a.

The edge areas NA can further include the hole-injecting dummy layer 119a contacting the lower surface of the first common layer extension 120a, as exemplarily shown in FIG. 4A.

The conductivity improvement layer 119 b and the hole-injecting dummylayer 119 a can be formed of the same material, or a material of thehole-injecting dummy layer 119 a can be selected from the point of viewof stabilized interfacial properties with the first electrode 110(referring to FIG. 2 ) and hole injection transmission, and a materialof the conductivity improvement layer 119 b can be selected from thepoint of view of location of the conductivity improvement layer 119 b onthe first common layer extension 120 a outside the first common layer120 and reduction in contact resistance with an element located thereon.

The second common layer 150 and the second common layer extension 150 ainclude a plurality of layers, and the second electrode extension 160 ain the edge areas NA is located closer to the edges of the edge areas NAthan the respective layers of the second common layer extension 150 a.

FIGS. 5A and 5B are respectively a plan view and a cross-sectional viewillustrating the edge areas of the light emitting display device inaccordance with the comparative example.

As exemplarily shown in FIGS. 5A and 5B, in the edge areas NA of thelight emitting display device in accordance with the comparativeexample, common layers, i.e., a hole transport layer 20, a hole blockinglayer 50, an electron transport layer 55 and a second electrode 60, areformed on a bank 15 such that widths thereof are gradually increased inthe upward direction.

In the light emitting display device in accordance with the comparativeexample, the lower position a layer is located at, the higher resistancethe layer has, and thus, when the lower layer contacts the secondelectrode 60, the resistance of the second electrode 60 is increased. Inorder to solve such a problem, the layers are stacked such that thewidths thereof in the edge areas are gradually increased in the upwarddirection. That is, as exemplarily shown in FIG. 5A, the hole transportlayer 20 has a first interval c, the hole blocking layer 50 and theelectron transport layer 55 respectively have margins S1 and S2, amargin M in consideration of interlayer misalignment among these commonlayers is provided, and the second electrode has a second intervalgreater than the margin M.

As such, the light emitting display device in accordance with thecomparative example requires intervals between common layer extensionsin the edge areas, and thus the size of the edge areas is increased.

Further, if the respective common layers are formed regardless of theseprocess margins, in severe cases, the hole transport layer 20 cancontact the second electrode 60, and thereby, contact resistance of thesecond electrode 60 can be remarkably increased.

In Table 1, such an abnormal structure in which the hole transport layer20 and the second electrode 60 contact in the edge areas due tointerlayer warpage generated in processes of the light emitting displaydevice in accordance with the comparative example will be compared to anormal structure. If the hole blocking layer 50 and the electrontransport layer 55 do not have the margins S1 and S2 in the edge area orthe edges of the hole blocking layer 50 and the electron transport layer55 are located farther inward than the edge of the hole transport layer20 due to a problem in interlayer alignment, the hole transport layer 20contacts the second electrode 60 and thus causes increase in theresistance of the second electrode 60, and thereby driving voltage todrive an organic light emitting diode including the second electrode 60is raised, as shown in Table 1. Further, contact between the holetransport layer 20 having high resistance and the second electrode 60lowers luminance even at a high driving voltage.

TABLE 1 Driving Color Color voltage Luminance coordinate coordinateCondition (V) (Cd/A) CIEx CIEy Normal 4.5 5.0 0.142 0.093 structureAbnormal 8.5 1.5 0.142 0.096 structure

FIG. 6A is a photograph representing the light emitting display devicein accordance with the comparative example in normal driving of bluelight emitting diodes, and FIG. 6B is a photograph representing thelight emitting display device in accordance with the comparative examplein abnormal driving of blue light emitting diodes, when the electrontransport layer having a smaller area than that of the hole transportlayer is formed in the edge areas and thus the hole transport layerdirectly contacts the second electrode. As exemplarily shown in FIG. 6B,when abnormal driving, blue light leakage due to abnormal driving occursin a region, where the second electrode and a first common layer havinghigh resistance (i.e., the hole transport layer) directly contact, atthe edge of the active area.

FIG. 7 is a cross-sectional view illustrating a configuration of edgeareas of a light emitting display device in accordance with a secondembodiment of the present invention.

As exemplarily shown in FIG. 7 , in the edge areas of the light emittingdisplay device in accordance with the second embodiment of the presentinvention, a hole-injecting dummy layer is omitted and only aconductivity improvement layer 215 is provided, as compared to the lightemitting display device in accordance with the first embodiment of thepresent invention shown in FIG. 4A. In this case, lower portions of afirst common layer 120 (referring to FIG. 2 ) in the active area AA anda first common layer extension 120 a in the edge areas NA can include ahole-transporting material as a dopant. In the same manner as theabove-described light emitting display device in accordance with thefirst embodiment, in the light emitting display device in accordancewith the second embodiment, the conductivity improvement layer 215 isformed such that the edge of the conductivity improvement layer 215coincides with the edge of the first common layer extension 120 a, andthus a second electrode extension 260 contacts the side of theconductivity improvement layer 215 having low resistance and thus raisein the resistance of the second electrode extension 260 and a secondelectrode connected thereto can be overcome. Also, even if a secondcommon layer extension 150 a is formed farther inward than the firstcommon layer extension 120 a, a second electrode extension 260 cancontact the side and upper surface of the conductivity improvement layer215 having low resistance, thus increment of contact area between thesecond electrode extension 260 and the conductivity improvement layer215 can prevent the resistance of the second electrode extension 260 anda second electrode connected thereto.

A principle of preventing raise in the resistance of the secondelectrode through the conductivity improvement layer 119 b in the lightemitting display device of the present invention will be described.

FIGS. 8A to 8C are cross-sectional views illustrating measurement ofsheet resistances of light emitting display devices in accordance withfirst to third test examples, and FIG. 9 is a graph representing thesheet resistances of the light emitting display devices in accordancewith the first to third test examples. Further, FIGS. 10A to 10C areband diagrams of the light emitting display devices in accordance withthe first to third test examples.

In the first to third test examples, as exemplarily shown in FIGS. 8A to8C, a first detection electrode 500 a and a second detection electrode500 b were prepared at both ends of the upper surface of each ofsubstrates 1000. Further, as exemplarily shown in FIGS. 8A and 8B, afirst layer formed of a first material 600 a used as a first commonlayer 120 and a second layer formed of a second material 600 b used as ap-type dopant were formed on the substrates 1000 of the first and secondtest examples. Further, as exemplarily shown in FIG. 8C, a third layerformed of a mixture 600 c of a hole-transporting material HTL to formthe first common layer 120 and a p-type dopant was formed on thesubstrate 1000 of the third test example. The p-type dopant is the samematerial as the second material 600 b of FIG. 8B, and employs one of thecompounds expressed as the above-described chemical formulas 1 to 4. Inthe first to third test examples, the material layers formed on therespective substrates 1000 had the same total thickness of 100 Å. In thethird test example, the content of the p-type dopant was 1 wt % to 5 wt% of the hole-transporting material HTL.

When current flows by applying a voltage difference between the firstdetection electrode 500 a and the second detection electrode 500 b ineach of the first and third test examples, sheet resistance of thesecond layer formed of the second material 600 b of the second testexample was 9E+11Ω/□, sheet resistance of the third layer formed of themixture 600 c of the third test example was 5E+11Ω/□ which ismeasurable, but sheet resistance the first layer formed of the firstmaterial 600 a of the first test example was excessively high to beexceed the measurement limit of a detector and thus cannot be measuredwith the detector.

Further, through the above-described test, it can be understood that, ifthe layer formed of the mixture 600 c acquired by mixing the secondmaterial (p-type dopant) 600 b with the material HTL 600 a of the firstcommon layer having high resistance is provided as in the light emittingdisplay device of the present invention, total resistance is reduced, ascompared to the case in which the layer formed of the second material600 b, i.e., a conductive material, alone is provided.

The reason for this is that the layer formed of the first material 600a, i.e., the hole-transporting material, alone has low electron mobilitybut, in the layer formed of the mixture 600 c of the third test example,a process of filling electron vacancies with holes is repeated due toelectron withdrawing characteristics of the p-type dopant, and the layerformed of the mixture 600 c has improved electron mobility as comparedto the layer formed of the p-type dopant 600 b alone and thus improvesentire conductivity.

Particularly, through the above-described test examples, it can beunderstood that the layer formed of the mixture 600 c including a smallamount of the p-type dopant having high conductivity, i.e., the secondmaterial 600 b, within the hole-transporting first material 600 a canlower resistance, as compared to the layer formed of the first material600 a alone or the layer formed of the p-type dopant 600 b. That is, itcan be expected that, if the conductivity improvement layer 119 bincluding the p-type dopant having an small thickness is provided on thefirst common layer 120, as in the light emitting display device of thepresent invention, the resistance of the second electrode 160 iseffectively lowered.

The first material can employ any material which is used to form ahole-transporting common layer, and the second material can employ oneof the compounds expressed as chemical formulas 2 to 4 or any materialwhich has p-type dopant characteristics equivalent thereto.

FIGS. 10A to 10C are band diagrams of the light emitting display devicesin accordance with the first to third test examples, in which the firstand second electrodes 110 and 160 are substituted for the first andsecond detection electrodes 500 a and 500 b in the first to third testexamples of FIGS. 8A to 8C, in terms of electron and hole mobilities oforganic light emitting diodes.

As exemplarily shown in FIG. 10A, when the layer formed of the firstmaterial 600 a is provided between the first electrode 110 and thesecond electrode 160 of the organic light emitting diode, a differencebetween a first LUMO level L1 of the first material 600 a and a workfunction of the first electrode 110 is excessively high, and thus, evenif a potential difference is applied between the first and secondelectrodes 110 and 160, an energy barrier from the first material 600 ato the first electrode 110 is excessively high and flow of electrons isalmost impossible.

As exemplarily shown in FIG. 10B, when the layer formed of the secondmaterial 600 b having a second LUMO level L2, which is low to be similarto the work function of the first electrode 110, such as a p-typedopant, is provided between the first electrode 110 and the secondelectrode 160 of the organic light emitting diode, electrons flow viathe low second LUMO level L2 and thus conductivity can be raised.

As exemplarily shown in FIG. 10C, when the layer formed of the mixture600 c acquired by mixing the second material (p-type dopant) 600 b withthe material (hole-transporting layer: HTL) is provided between thefirst electrode 110 and the second electrode 160 of the organic lightemitting diode, as in the light emitting display device of the presentinvention, the layer formed of the mixture 600 c steals electrons fromthe first material (HTL) 600 a due to electron withdrawingcharacteristics of the second material (p-type dopant) 600 b, andthereby, the first material (HTL) 600 a relatively lacks electrons,holes are generated in the first material (HTL) 600 a, and thus carriermobility to the light emitting diodes and conductivity of the lightemitting diodes are increased.

Hereinafter, a method for manufacturing the light emitting displaydevice in accordance with an embodiment of the present invention will bedescribed.

First, as exemplarily shown in FIGS. 1B and 2 , the substrate 100 havingthe active area AA having a plurality of subpixels and the edge areas NAaround the active area AA is prepared.

The thin film transistor array including thin film transistors TFTscorresponding to the respective subpixels is formed on the substrate100.

Thereafter, the inorganic protective film 108 and the organic protectivefilm 109 are sequentially deposited on the thin film transistor arrayand are selectively removed to expose the drain electrodes 106 of thethin film transistors TFTs, and the first electrodes 110 connected tothe drain electrodes 106 are provided.

The features of the present invention can be characterized in that thefirst common layer 120/the first common layer extension 120 a, theconductivity improvement layer 119 b and the hole-injecting dummy layer119 a are formed in the same chamber through the same process, and thusdescriptions of formation thereof will be focused upon. FIGS. 11A to 11Eare process views illustrating a method for forming the first commonlayer and the conductivity improvement layer of the light emittingdisplay device in accordance with the present invention, and FIGS. 12Ato 12E are views illustrating arrangements of deposition sourcesrespectively used in operations of FIGS. 11A to 11E. FIG. 13A is across-sectional view illustrating a structure of the edge areacorresponding to deposition materials in the initial stage of adeposition process, after completion of the operation of FIG. 11E, FIG.13B is a cross-sectional view illustrating a structure of the activearea, after completion of the operation of FIG. 11E, and FIG. 13C is across-sectional view illustrating a structure of the edge areacorresponding to the deposition materials in the final stage of thedeposition process, after completion of the operation of FIG. 11E.

Formation of the first common layer 120, the conductivity improvementlayer 119 b and the hole-injecting dummy layer 119 a (Operations S1-S5)is carried out using the same mask 540 in the same chamber 800.

As exemplarily shown in FIG. 11A, a first common layer materialdeposition source 512 and first and second p-type dopant materialdeposition sources 511 and 513 located at both sides thereof, which candeposit respective components thereof by vaporization through cruciblesprovided thereunder, are prepared in the chamber 800. As exemplarilyshown in FIG. 12A, the first common layer material deposition source 512and the first and second p-type dopant material deposition sources 511and 513 respectively have a plurality of supply openings 512 a, 511 aand 513 a which are arranged in a row, and the supply openings 511 a and513 a of the first and second p-type dopant material deposition sources511 and 513 can be selectively opened and closed by shutters 530 and 535(in FIG. 11C) according to the sequence of the deposition process.

Further, a common mark 540 having an opening having a size to cover thewidth of the active area AA and the first intervals c at both ends ofthe width of the active area AA in which the first common layerextension 120 a can be formed, as described above referring to FIG. 1B,is provided above the first common layer material deposition source 512and the first and second p-type dopant material deposition sources 511and 513.

Inner angle correction plates 521 and 522 to define a deposition angleof the materials from the deposition sources 512, 511 and 513 which aredeposited on the substrate 100 are further provided between the uppersurfaces of the first common layer material deposition source 512 andthe first and second p-type dopant material deposition sources 511 and513 and the lower surface of the common mask 540. The inner anglecorrection plates 521 and 522 can be provided according to therespective deposition sources 512, 511 and 513, or can be provided atboundaries among the deposition sources 512, 511 and 513.

Further, a substrate 2000 provided with first electrodes 110 connectedto the drain electrodes 106 of the above-described thin film transistorsis provided above the common mask 540, and the deposition process inwhich lower deposition materials are deposited onto the substrate 2000through the opening of the common mask 540 is carried out, while thesubstrate 2000 is moved.

The substrate 2000 has an active area AA and edge areas NA (or BZP)around the active area AA, as exemplarily shown in FIG. 1B.

Further, although not shown in the drawings for convenience, the firstelectrodes 110 (referring to FIG. 2 ) are formed on the thin filmtransistor array in the respective subpixels.

Here, when the substrate 2000 is moved in the rightward direction, asexemplarily shown in FIG. 11A, the deposition materials are depositedonto the substrate 200 from right to left. Although not shown in thedrawings, when the substrate 2000 is moved in the leftward direction,deposition is carried out on the substrate 200 from left to right.

At an initial scanning stage of the deposition materials, the supplyopenings 511 a and 512 a of the first p-type dopant material depositionsource 511 and the first common layer material deposition source 512 areopened, the supply openings 513 a of the second p-type dopant materialdeposition source 513 are closed with a first shutter 530, and then thedeposition process is carried out.

As exemplarily shown in FIG. 11A, when the substrate 2000 is moved inthe rightward direction and primarily corresponds to the opening of thecommon mask 540, the hole-injecting dummy layer 119 a alone is formed insome of the edge areas of the substrate 2000 by supplying the depositionmaterial from the first p-type dopant material deposition source 511located at the leftmost position through the opening of the common mask540. When the hole-injecting dummy layer 119 a is formed, the supplyopenings 511 a and 512 a of the first p-type dopant material depositionsource 511 and the first common layer material deposition source 512 areopened, and thus deposition of the hole-injecting dummy layer 119 a iscarried out by partially mixing a p-type dopant material and a firstcommon layer material supplied from the first p-type dopant materialdeposition source 511 and the first common layer material depositionsource 512.

As exemplarily shown in FIG. 11A, since the p-type dopant material fromthe first p-type dopant material deposition source 511 is first suppliedto an advancing side of the substrate 2000, the hole-injecting dummylayer 119 a includes the p-type dopant material mixed with the firstcommon layer material. When the substrate 2000 of FIG. 11A firstcorresponds to a deposition material supply unit, in order to secure adesignated thickness of the hole-injecting dummy layer 119 a, a supplyamount of the p-type dopant material from the first p-type dopantmaterial deposition source 511 can be increased at an initial stage ofrightward movement of the substrate 2000.

Subsequently, as exemplarily shown in FIGS. 11B and 12B, the substrate2000 is continuously moved in the rightward direction, and a firstcommon material layer 1200 formed of the first common layer material isformed on the substrate 2000 provided with the hole-injecting dummylayer 119 thereon. The first common material layer 1200 includes thefirst common layer 120 in the active area AA and the first common layerextension 120 a in the edge areas NA, as described above referring toFIGS. 1A and 1B. The first common material layer 1200 is formed of thesame material to have the same thickness in both the active area AA andthe edge areas NA.

Since the amount of the first common layer material supplied from thefirst common layer material deposition source 512 is much greater thanthe amount of the p-type dopant material supplied from the first p-typedopant material deposition source 511, the first common material layer1200 can be formed. A supply region of the p-type dopant material fromthe first p-type dopant material deposition source 511 partiallyoverlaps a supply region of the first common layer material from thefirst common layer material deposition source 512 in the movingdirection of the substrate 2000, and thus the lower portion of the firstcommon material layer 1200 can include a small amount of the p-typedopant material.

After formation of the hole-injecting dummy layer 119 a and the firstcommon material layer 1200 in the entire area of the substrate 2000 orin the entire active area and some of the edge areas of the substrate200 has been completed, as such, the substrate 2000 is moved in theopposite direction, as exemplarily shown in FIG. 11C. Here, a secondshutter 535 is provided above the first p-type dopant materialdeposition source 511 so as to prevent supply of the p-type dopantmaterial from the first p-type dopant material deposition source 511. Inan initial stage of leftward movement of the substrate 2000, a p-typedopant material 1190 is deposited onto the upper surface of the firstcommon material layer 1200 in the left edge area (the edge area NA1 inFIG. 13A). Subsequently, as exemplarily shown in FIG. 11D, while thesubstrate 2000 is continuously moved in the leftward direction, a firstcommon layer material 120 b is deposited onto the active area. Here, asexemplarily shown in FIG. 12D, the second shutter 535 and the firstshutter 530 are provided above the first p-type dopant materialdeposition source 511 and the second p-type dopant material depositionsource 513 so that the first common layer material 120 b alone issupplied to the active area, and thus, the first common layer material120 b alone is deposited on the upper surface of the first commonmaterial layer 1200 in the active area AA without the p-type dopant.

Subsequently, as exemplarily shown in FIGS. 11E and 12E, when opening ofthe common mask 540 corresponds to the right edge area (the edge areaNA3 in FIG. 13C) of the substrate 2000, the openings 511 a of the firstp-type dopant material deposition source 511 are opened by removing thefirst shutter 535 above the first p-type dopant material depositionsource 511, and thus the p-type dopant material 1190 is deposited ontothe right edge area of the substrate 200.

Through the above formation process, the p-type dopant material 1190 andthe first common layer material 120 b are mixed and remain on the uppersurface of the first common layer extension 120 a in the edge areas andthus form the conductivity improvement layer 119 b, as exemplarily shownin FIGS. 13A and 13C, and the first common layer material 120 b aloneremains in the active area, as exemplarily shown in FIG. 13B.

The initial shapes of the conductivity improvement layer 119 b locatedin the first and third edge areas NA1 and NA3 located at positionsopposite to each other in the moving direction of the substrate 200 canbe different according to the position of the layer formed of the p-typedopant material 1190, as exemplarily shown in FIGS. 13A and 13C.

Here, as exemplarily shown in FIGS. 13A and 13C, although the positionof the layer formed of the p-type dopant material 1190 is varied, thefirst common material layer 120 a substantially has a large thickness ofabout 200-1000 Å, and the layer formed of the p-type dopant material1190 and the layer formed of the first common layer material 120 b whichare located on the first common material layer 120 a have a totalthickness of less than 50 Å after stacking of the two layers, and haveeffects of the conductivity improvement layer 119 b in which the p-typedopant material 1190 is mixed with the first common layer material 120b, after a specific period of time passes in the chamber 800. Further,after the substrate 2000 is unloaded from the chamber 800, cleaning iscarried out before a process of forming light emitting layers, and thusseparation from subsequent layers is possible.

Further, after the formation process shown in FIGS. 11A to 11E, thefirst common material layer 1200 and the layer formed of the firstcommon layer material 120 b, which are sequentially deposited in theactive area, are not discriminated from each other, thus forming asingle first common layer 120, as exemplarily shown in FIG. 13B.

In this case, the layer formed of the first common layer material 120 bis not provided but only the first common layer extension 120 a formedof the first common material layer 1200 remains under the conductivityimprovement layer 119 b in the first edge area NA1, and thus the firstcommon layer extension 120 a in the first edge area NA1 has a smallerthickness than the first common material layer 1200 in the active areaAA. On the other hand, as exemplarily shown in FIG. 13C, the layerformed of the first common layer material 120 b remains on the firstcommon layer extension 120 a in the third edge area NA3 corresponding toa first common layer material supply ending part, similarly to theactive area, and thus the layer formed of the first common layermaterial 120 b having the same thickness of the first common layer 120in the active area AA can remain in some of the edge areas NA.

For example, in the above-described deposition method of the lightemitting display device in accordance with the present invention, theconductivity improvement layer 119 b is formed by supplying aconductivity improving material corresponding to first common layermaterial supply starting part and ending part of the substrate 2000 (thefirst edge area and third edge area of the substrate 2000 opposite toeach other or the second edge area and fourth edge area of the substrate2000 opposite to each other) from the first common layer materialdeposition source, as exemplarily shown in FIG. 1B.

Thereby, a part or the entirety of the upper portion of the first commonlayer extension 120 a (in FIG. 1B) in the edge areas NA can be theconductive improvement layer 119 b. For example, as exemplarily shown inFIG. 1B, the conductivity improvement layer 119 b may not be formed onthe first common layer extension 120 located in the second and fourthedge areas NA2 and NA4. In this case, in the second and fourth edgeareas NA2 and NA4, the first common layer extension 120 a formed of thesame common layer material as the first common layer 120 in the activearea AA and having the same thickness of the first common layer 120 isprovided.

The first common layer 120 formed through the above process is formedintegrally with the first common layer extension 120 a having the firstinterval c (referring to FIG. 1B) in the edge areas, and the firstcommon layer extension 120 a protrudes from the first common layer 120in the active area AA by the first interval c.

Although, in the examples of the present invention, the conductivityimprovement layer 119 b and the hole-injecting dummy layer 119 a areformed of the same material, the conductivity improvement layer 119 band the hole-injecting dummy layer 119 a can be formed of differentmaterials by additionally disposing a hole injecting material depositionsource adjacent to the first common layer material deposition source 152to supply the first common layer material in the chamber 800.

After formation of the conductivity improvement layer 119 b, the lightemitting layers 140: 140 r, 140 g and 140 b are formed in the respectivepixels RP, GP and BP.

Thereafter, the second common layer 150 having a greater size than theactive area AA is provided on the light emitting layers 140: 140 r, 140g and 140 b. A part of the second common layer 150 formed outside theactive area AA is defined as the second common layer extension 150 a.

Thereafter, the second electrode 160 including the second electrodeextension 160 a having the second process margin (the second interval a)in the edge areas NA to cover at least the first common layer 120 andthe first common layer extension 120 a is formed on the second commonlayer 150 and the second common layer extension 150 a.

The second interval a is provided outside the first interval c and thusthe second electrode extension 160 a extends to the outermost positionout of the elements of the light emitting diode. For example, the secondinterval a can have a distance of 100 μm or more outward from the edgeof the first interval c, and the edge of the second common layerextension 150 a can be located between the first common layer extension120 a and the second electrode extension 160 a.

As described above, the light emitting display device in accordance withone or more embodiments of the present invention further includes theconductivity improvement layer corresponding to the edge of the firstcommon layer having high resistance, thus preventing raise in resistancein the edge areas.

Further, if common layers formed subsequent to formation of the firstcommon layer and the conductivity improvement layer have no processmargins, the second electrode contacts the conductivity improvementlayer other than the first common layer in the edge areas, and thusconductivity of the second electrode can be maintained and reduction inluminance or abnormal driving in a specific region can be prevented.

In addition, in the method for manufacturing the light emitting displaydevice in accordance with one or more embodiments of the presentinvention, even if a mask used to form the conductivity improvementlayer is not additionally provided, the conductivity improvement layercan be restrictively formed in the edge areas by causing theconductivity improving material deposition sources to selectivelycorrespond to the substrate at a starting time and an ending time offirst common layer material supply. For instance, without addition of orchange in deposition, masks the light emitting display device can secureuniform luminescent characteristics due to selective formation of theconductivity improvement layer.

Further, the light emitting display device in accordance with one ormore embodiments of the present invention can have uniform luminancethroughout the entirety of the active area without increase inresistance even if the conductivity improvement layer contacts thesecond electrode located on the conductivity improvement layer, thesecond common layer(s) formed after formation of the conductivityimprovement layer can have a degree of freedom, process margins thereofin the edge areas can be reduced or omitted, and thus a narrow bezel canbe achieved.

Moreover, the light emitting display device in accordance with one ormore embodiments of the present invention can form the second commonlayer having a reduced process margin or no process margin, minimize thearea occupied by of the second electrode located on the second commonlayer outside the first common layer, and thus reduce a region in whichorganic common layers are provided, in the edge areas. Therefore, someof the edge areas which do not overlap the organic common layers and thesecond electrode can be secured as regions to mount various parts, suchas a camera hole, a printed circuit film, etc. thereon, and thus thelight emitting display device in accordance with the present inventioncan be applied to various designs.

In addition, the light emitting display device in accordance with one ormore embodiments of the present invention can define a process margin ofthe light emitting diodes shown in FIGS. 1A and 1B as only the sum ofthe first interval c of the first common layer extension 120 a and thesecond interval a of the second electrode extension 160 a, thusremarkably reducing the process margin generated in the depositionprocess of the light emitting diodes.

As apparent from the above description, a light emitting display deviceand a method for manufacturing the same in accordance with one or moreembodiments of the present invention have advantages and effects asfollows.

First, the light emitting display device in accordance with one or moreembodiments of the present invention further includes a conductivityimprovement layer corresponding to the edge of a first common layerhaving high resistance, thus preventing raise in resistance in edgeareas.

Second, if common layers formed subsequent to formation of the firstcommon layer and the conductivity improvement layer have no processmargins, a second electrode contacts the conductivity improvement layerother than the first common layer in the edge areas, and thusconductivity of the second electrode can be maintained and reduction inluminance or abnormal driving in a specific region can be prevented.

Third, even if a mask used to form the conductivity improvement layer isnot additionally provided, the conductivity improvement layer can berestrictively formed in the edge areas by causing conductivity improvingmaterial deposition sources to selectively correspond to a substrate ata starting time and an ending time of first common layer materialsupply. That is, without addition of or change in deposition, masks thelight emitting display device can secure uniform luminescentcharacteristics due to selective formation of the conductivityimprovement layer.

Fourth, the light emitting display device in accordance with one or moreembodiments of the present invention can have uniform luminancethroughout the active area without increase in resistance even if theconductivity improvement layer contacts the second electrode located onthe conductivity improvement layer, second common layer(s) formed afterformation of the conductivity improvement layer can have a degree offreedom, process margins thereof in the edge areas can be reduced oromitted, and thus a narrow bezel can be achieved.

Fifth, the light emitting display device in accordance with one or moreembodiments of the present invention can form the second common layerhaving a reduced process margin or no process margin, minimize the areaoccupied by the second electrode located on the second common layeroutside the first common layer, and thus reduce a region in whichorganic common layers are provided, in the edge areas. Therefore, someof the edge areas which do not overlap the organic common layers and thesecond electrode can be secured as regions to mount various parts, suchas a camera hole, a printed circuit film, etc. thereon, and thus thelight emitting display device in accordance with the present inventioncan be applied to various designs.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method for manufacturing a light emittingdisplay device, the method comprising: preparing a substrate having anactive area in which a plurality of subpixels are disposed, and an edgearea surrounding the active area; forming a first electrode on eachsubpixel in the active area; forming a first common layer on thesubstrate in which the first electrode is formed, the first common layerincluding a first covering region covering an entirety of the activearea and a first surrounding region surrounding the first coveringregion on a portion of the edge area adjacent to the active area;forming a conductivity improvement layer overlapping with the edge areaon the first surrounding region of the first common layer; forming alight emitting layer on each subpixel of the substrate in which thefirst common layer is formed; forming a second common layer on thesubstrate in which the light emitting layer is formed, the second commonlayer including a second covering region overlapping with the entiretyof the active area and a second surrounding region surrounding thesecond covering region on the conductivity improvement layer; andforming a second electrode on the substrate in which the second commonlayer is formed, the second electrode covering the first common layerand the second common layer, wherein the second electrode is formed tobe in contact with the conductivity improvement layer in the edge area.2. The method according to claim 1, wherein: the first surroundingregion has a first width; and the second surrounding region has a secondwidth smaller than the first width.
 3. The method according to claim 1,wherein: the conductivity improvement layer is formed in a same chamberas the first common layer.
 4. The method according to claim 3, whereinforming the first common layer and the conductivity improvement layerincludes: positioning a first deposition source containing a materialfor forming the first common layer in a chamber; positioning a seconddeposition source containing a p-type dopant in the chamber; arranging amask on the first deposition source and the second deposition source,the mask having a hole overlapping with the first deposition source andthe second deposition source; moving the substrate in which the firstelectrode is formed in a direction on the mask; forming the first commonlayer on the active area and the edge area of the substrate using thefirst deposition source, in a state in which the second depositionsource is closed by a shutter; and forming the conductivity improvementlayer on the first common layer of the edge area, in a state in whichthe first deposition source and the second deposition source are opened,and wherein the second deposition source is arranged side by side withthe first deposition source.
 5. The method according to claim 4, whereinthe conductivity improvement layer is formed by mixing the material forforming the first common layer and the p-type dopant.
 6. The methodaccording to claim 3, further comprising forming a hole injecting dummylayer on the substrate in which the first electrode is formed, beforethe first common layer, wherein the hole injecting dummy layer is formedin the same chamber as the first common layer and the conductivityimprovement layer.
 7. The method according to claim 6, wherein theforming the hole injecting dummy layer, the first common layer and theconductivity improvement layer includes: positioning a first depositionsource containing a material for forming the first common layer in achamber; positioning a second deposition source containing a firstp-type dopant in the chamber; positioning a third deposition sourcecontaining a second Hype dopant in the chamber; arranging a mask on thefirst deposition source, the second deposition source and the thirddeposition source, the mask having a hole overlapping with the firstdeposition source, the second deposition source and the third depositionsource; moving the substrate in which the first electrode is formed in adirection on the mask; forming the hole injecting dummy layer and thefirst common layer on the active area and the edge area of thesubstrate, in a state in which the first deposition source and the thirddeposition source are opened, and the second deposition source is closedby a shutter; and forming the conductivity improvement layer on the edgearea of the substrate, in a state in which the first deposition sourceand the second deposition source are opened and the third depositionsource is closed by a shutter, and wherein the first deposition sourceis arranged between the second deposition source and the thirddeposition source.
 8. The method according to claim 7, wherein the holeinjecting dummy layer is formed by mixing the material for forming thefirst common layer and the second p-type dopant contained in the thirddeposition source, and wherein the conductivity improvement layer isformed by mixing the material for forming the first common layer and thefirst p-type dopant contained in the second deposition source.